That's what mine looks like.It was a one piece:
My grandmother had a doorbell like that on her back door. It was an old Victorian house with apron porches. The doorbell was round and in the middle of the door. You turned a lever in the middle like a key to made it ring.@neely
The front door of that house had a doorbell that was hand cranked.
Her house was electrified long after it was built, so the switches were buttons you pushed. There was a cord that swung to the ceiling with a lone electric bulb hanging from it. Talk about the spooky shadows it created.